Quantitative vibrometry and electrophysiological assessment in screening for carpal tunnel syndrome among industrial workers: a comparison

Pain mechanisms in carpal tunnel syndrome: a systematic review and meta-analysis of quantitative sensory testing outcomes

ABSTRACT

Carpal tunnel syndrome (CTS) is the most common nerve compression in the arm. A mix of peripheral and central contributions on quantitative sensory testing (QST) has been reported in the literature. Thus, this systematic review or meta-analysis aimed to identify the dominant sensory phenotype and draw conclusive evidence about the presence of central sensitization (CS) in CTS. Based on an a priori published protocol and using PRISMA guidelines, 7 databases were searched (Embase, Web of Science, Scopus, PubMed, SAGE, EBSCOhost, and ProQuest). Eligible studies compared the QST findings of individuals with subacute and chronic CTS with those of healthy controls through thermal, mechanical, and vibration detection thresholds; thermal, pressure, and mechanical pain thresholds; mechanical pain sensitivity; presence of allodynia; wind-up ratio; and conditioned pain modulation. Thirty-seven studies were included in the qualitative analysis. Results showed a significant loss of all detection thresholds of hand median nerve territories and hand extramedian areas (little finger and hand dorsum) in CTS (P < 0.05) but no significant difference (P > 0.05) in wind-up ratio, cold, heat, or mechanical pain thresholds of the median nerve territories. Furthermore, there was a significant increase in mechanical pain sensitivity in median nerve territories and remotely in the forearm (P < 0.05) and a significant gain in pressure and heat pain thresholds in the carpal area (P < 0.05). Conditioned pain modulation was impaired in CTS. Hypoesthesia and increased thermal and mechanical pain ratings are the dominant sensory phenotype with inconclusive evidence about CS in CTS due to the heterogenous results of thermal and mechanical pain thresholds.

Effects of carpal tunnel syndrome on adaptation of multi-digit forces to object texture

OBJECTIVE

The ability to adapt digit forces to object properties requires both anticipatory and feedback-driven control mechanisms which can be disrupted in individuals with a compromised sensorimotor system. Carpal tunnel syndrome (CTS) is a median nerve compression neuropathy affecting sensory and motor function in a subset of digits in the hand. Our objective was to examine how CTS patients coordinate anticipatory and feedback-driven control for multi-digit grip force adaptation.

METHODS

We asked CTS patients and healthy controls to grasp, lift, and hold an object with different textures.

RESULTS

CTS patients effectively adapted their digit forces to changes in object texture, but produced excessive grip forces. CTS patients also produced larger peak force rate profiles with fewer modulations of normal force prior to lift onset than did controls and continued to increase grip force throughout the lift whereas forces were set at lift onset for the controls.

CONCLUSIONS

These findings suggest that CTS patients use less online sensory feedback for fine-tuning their grip forces, relying more on anticipatory control than do healthy controls.

SIGNIFICANCE

These characteristics in force adaptation in CTS patients indicate impaired sensorimotor control which leads to excessive grip forces with the potential to further exacerbate their median nerve compression.

Feasibility and safety of antegrade radial artery cannulation

BACKGROUND AND OBJECTIVE

The purpose of this study was to compare thrombosis rates in antegrade (catheter directed toward the hand) versus retrograde (catheter directed toward the elbow) cannulation of the radial artery. Our secondary objectives were to compare these two techniques in terms of success rate, differences in noninvasive versus invasive blood pressure measurement and complications.

METHODS

After obtaining the approval of the local ethics committee and written informed consent, the patients were randomly allocated to the antegrade (group A, n=60) or retrograde (group R, n=60) groups. Arterial thrombosis was evaluated by ultrasonography in each patient. Noninvasive and invasive blood pressure measurements and complications were recorded. Data were analysed using Student's t-test, the Mann-Whitney U-test, the categorical chi test, Fisher's exact test and Bland-Altman analysis.

RESULTS

Thrombosis rates were similar between groups. The success rates for cannulation were 86.7 and 96.7% in the antegrade and retrograde groups, respectively (P<0.05). Complication rates were similar between groups. Very significant correlation was observed between the invasive and noninvasive methods when simultaneously measuring arterial systolic, diastolic and mean blood pressure. However, antegrade arterial measurements were consistently lower than those obtained via noninvasive methods.

CONCLUSIONS

We conclude that antegrade radial artery cannulation has no advantage over the retrograde approach in terms of reducing thrombosis, but it can be used in cases when the retrograde approach has failed.

Effects of prolonged wrist flexion on transmission of sensory information in carpal tunnel syndrome

Carpal tunnel syndrome presents a constellation of symptoms which include discomfort (eg, pain, paraesthesia) and diminished sense of touch. This exploratory study simultaneously measured changes in tactile threshold and discomfort ratings during prolonged wrist flexion in symptomatic patients from a rehabilitation clinic and from a control population. Prolonged (15 min) wrist flexion significantly increased tactile threshold and discomfort ratings above baseline levels in both symptomatic and control populations. Sixty-two percent of the symptomatic sample was found to have abnormal conduction latency. Tactile threshold in symptomatic subjects with normal conduction latency (n = 13) did not differ significantly from control subjects (n = 36) at baseline but showed significant elevation during wrist flexion. In contrast, subjects with abnormal conduction latency (n = 21) exhibited significant elevation relative to control subjects at baseline and throughout wrist flexion as well as a slower recovery after flexion. Conduction latency correlated with baseline (r = .52, P < .0001) and 15-min (r = .67, P < .0001) tactile threshold for the entire subject population, as well as 15-min threshold (r = .53, P = .013) for the subpopulation with abnormal conduction latency. At 2.5 min after flexion, correlation was significant for whole (r = .64, P < .0001) and abnormal conduction latency (r = .58, P = .0063) samples. Regression slope of tactile threshold versus conduction latency was significantly greater than zero and did not differ significantly from linearity. The study demonstrates that increases in mechanosensory threshold and discomfort ratings during prolonged wrist flexion are more profound (and recovery less rapid) in patients with electrophysiologic evidence of injury.

PERSPECTIVE

This study demonstrates a provocative procedure that enhances the symptoms of carpal tunnel syndrome. This measure may help clinicians discriminate median nerve compression from other types of peripheral nerve injury and help researchers investigate the impact of mechanical stress, tissue compression, and vascular stasis on compression-related neuropathy.

Evaluation of work-related carpal tunnel syndrome

OBJECTIVES

Carpal tunnel syndrome (CTS) is common in the industrial setting but there are still some advocates who argue that CTS is not a work related problem. There are also controversies about the proper way to establish the diagnosis and whether screening for CTS in the industrial setting is warranted.

METHODS

A comprehensive literature review.

RESULTS

The literature does demonstrate that the prevalence of CTS in the industrial setting is significantly higher than in the general population. Numerous epidemiologic studies have identified independent risk factors, which include repetitiveness of work, forceful exertions, mechanical stress, posture, and vibration as well as several personal co-factors. The strength of these associations are discussed. The diagnostic criteria for establishing work-related CTS are discussed as well as the effectiveness of various screening methods that are commonly used in the workplace. The sensitivity and specificity of nerve conduction studies to establish or confirm the diagnosis of CTS is presented along with normative data for the industrial worker.

CONCLUSIONS

CTS has both work-related and personal risk factors. The diagnosis is best established using a combination of history, symptom distribution and confirmation using the relative latency of median sensory testing using normative data. Screening for CTS in the industrial setting has questionable benefit.

Vibrotactile sense in patients with different upper limb disorders compared with a control group

BACKGROUND

Upper limb disorders (ULDs) are common, and so are the difficulties with regard to their specific diagnoses. According to diagnostic consensus criteria, specific diagnoses include neuropathy and muscular- and connective-tissue disorders (MCDs). There is a need for valid objective diagnostic tools to reveal underlying mechanisms for specific diagnoses.

OBJECTIVE

To investigate the possible differences in vibration perception threshold (VPT) and tolerance to suprathreshold stimulation (STS) between controls and specific diagnostic ULD patient groups with uni- and bilateral neuropathy and/or MCD.

METHODS

In 161 ULD patients and 40 controls, the VPT of the median, ulnar, and radial nerves innervating the hand was examined by vibrometry using the "method of limits". The tolerance to STS of the anterior forearm was tested in 128 of the patients and all controls.

RESULTS

The ULD patients in all diagnostic groups had significantly higher VPT (P<0.05) in all the nerves in limbs, with and without diagnoses compared with controls. Only patient groups defined with neuropathy demonstrated significantly higher VPT in the limb with diagnoses compared with the contralateral limb without diagnoses. The highest VPTs were found in the patient group with unilateral neuropathy and MCD, and for the radial nerve, VPT was significantly higher than that for patients with unilateral MCD alone. These findings were confirmed by almost similar findings in STS responses.

CONCLUSIONS

The ULD patients generally demonstrated increased VPT compared with controls, indicating a neurogenous component independent of specific ULD diagnosis. Contralateral significant findings in limbs without diagnoses compared with controls indicate central neurogenous affection and/or the possibility of certain exposures elevating VPT before a positive status of a limb diagnosis is attained. Significantly higher VPT values in limbs with neuropathy diagnoses compared with limbs without and not in MCD alone, may indicate peripheral sensibilization or nerve affection only in the group with a specific diagnosis of neuropathy. These findings underline the importance of specific diagnoses among ULD patients.

Digital vibration threshold testing and ergonomic stressors in automobile manufacturing workers: a cross-sectional assessment

Upper extremity musculoskeletal disorders (UEMSDs) comprise a large proportion of work-related illnesses in the USA. Physical risk factors including manual force and segmental vibration have been associated with UEMSDs. Reduced sensitivity to vibration in the fingertips (a function of nerve integrity) has been found in those exposed to segmental vibration, to hand force, and in office workers. The objective of this study was to determine whether an association exists between digital vibration thresholds (VTs) and exposure to ergonomic stressors in automobile manufacturing. Interviews and physical examinations were conducted in a cross-sectional survey of workers (n = 1174). In multivariable robust regression modelling, associations with workers' estimates of ergonomic stressors stratified on tool use were determined. VTs were separately associated with hand force, vibration as felt through the floor (whole body vibration), and with an index of multiple exposures in both tool users and non-tool users. Additional associations with contact stress and awkward upper extremity postures were found in tool users. Segmental vibration was not associated with VTs. Further epidemiologic and laboratory studies are needed to confirm the associations found. The association with self-reported whole body vibration exposure suggests a possible sympathetic nervous system effect, which remains to be explored.

Clinical diagnosis of carpal tunnel syndrome: a systematic review

The purposes of this systematic review were to examine the properties of clinical tests used in the diagnosis of carpal tunnel syndrome (CTS) and to provide estimates of their sensitivity and specificity. A literature search was conducted using two databases-PubMed and the Cumulative Index to Nursing and Allied Health Literature (CINAHL)-from 1986 to June 2003, and hand-searching reference lists of retrieved articles. Two reviewers evaluated the papers for quality using an evaluation tool developed by one of the authors. Estimates of sensitivity and specificity were determined by averaging values across studies weighted by sample size. Although 60 studies were reviewed in detail, many were of poor quality (mean quality score was 6.6 of 12, with only 15 of 60 obtaining a score of 8 or greater). The most frequently studied test was Phalen's, with an overall estimate of 68% sensitivity and 73% specificity. Next was Tinel's, with estimates of 50% and 77%, and then carpal compression, with estimates of 64% and 83% for sensitivity and specificity, respectively. Two-point discrimination and testing of atrophy or strength of the abductor pollicis brevis proved to be specific but not very sensitive. The estimates determined in this review should help therapists choose clinical tests with the appropriate balance of sensitivity and specificity required for diagnosing carpal tunnel syndrome in their specific clinical environments.

Tingling/numbness in the hands of computer users: neurophysiological findings from the NUDATA study

OBJECTIVES

To investigate whether tingling/numbness of the hands and fingers among computer users is associated with elevated vibration threshold as a sign of early nerve compression.

METHODS

Within the Danish NUDATA study, vibratory sensory testing with monitoring of the digital vibration threshold at seven frequencies on the second and fifth fingers of both hands was performed on 20 cases with unilateral tingling/numbness in the hands and fingers, and 20 gender- and age-matched controls. Both cases and controls were identified from questionnaire information about tingling/numbness at least once a week or daily within the last 3 months. Participants with more than slight muscular pain or disorders of the neck and upper extremities, excessive alcohol consumption, previous injuries of the upper extremities, or concurrent medical diseases were excluded. The two groups had a similar amount of work with mouse, keyboard, and computer.

RESULTS

Seven of the 20 cases (35%) had elevated vibration thresholds, compared with 3 of the 20 controls (15%); this difference was not statistically significant (chi2=2.13, P=0.14). Compared with controls, cases had increased perception threshold for all frequencies, but the difference was statistically significant for only 2 out of 14 measurements. Comparison between left and right hand threshold values within the case group did not show any significant difference at any frequency.

CONCLUSIONS

The results indicate that tingling/numbness of the hands and fingers among computer users cannot be explained by nerve compression.

Clinical and electrodiagnostic testing of carpal tunnel syndrome: a narrative review

Carpal Tunnel Syndrome (CTS) is a pressure-induced neuropathy that causes sensorimotor disturbances of the median nerve, which impair functional ability. A clear history that elicits relevant personal and work exposures and the nature of symptoms can lead to a high probability of a correct diagnosis. Hand diagrams and diagnostic questionnaires are available to provide structure to this process. A variety of provocative tests have been described and have variable accuracy. The Phalen's wrist flexion and the carpal compression tests have the highest overall accuracy, while Tinel's nerve percussion test is more specific to axonal damage that may occur as a result of moderate to severe CTS. Sensory evaluation of light touch, vibration, or current perception thresholds can detect early sensory changes, whereas 2-point discrimination changes and thenar atrophy indicate loss of nerve fibers occurring with more severe disease. Electrodiagnosis can encompass a variety of tests and is commonly used to assess the presence/severity of neuropathic changes and to preclude alternative diagnoses that overlap with CTS in presentation. The pathophysiologic changes occurring with different stages of nerve compression must be considered when interpreting diagnostic test results and predicting response to physical therapy management.

Quantitative vibration threshold testing in carpal tunnel syndrome: analysis strategies for optimizing reliability

Tuning forks and electronic vibrometers have been used to quantify vibration sensation thresholds, which are thought to be affected early in carpal tunnel syndrome (CTS). The purpose of this study was to identify a reliable testing procedure for a newly designed, computer-controlled vibrometer (PCV50; Ztech, Salt Lake City, UT). Fifty-two patients (mean age 48+/-8 years) with electromyographically confirmed CTS were tested on one occasion. The computer-controlled vibrometer, with a fixed frequency of 50 Hz, used stepwise changes in amplitude to determine vibration sensation threshold. Each patient had three vibrometer measures (trials) taken on the pulp of the third digit of their right and left hands during the first test session and were retested by a single repetition 40 to 60 minutes later (retest). Intraclass correlation coefficients (ICCs) were used to examine several data analysis strategies. The strategy that generated the highest ICCs for both the right and left hands assumed that the first trial was a learning or practice attempt, and compared the average of the second and third trials with the score from the second session (ICC=0.86 and 0.89, respectively). The computer-controlled vibrometer offered an easily administered, quantitative, and comfortable means to assess median nerve function. Using this reliable testing procedure will allow for additional investigations to determine its usefulness in the early detection and accurate quantification of CTS-related impairment.

Criteria for assessing pain and nonarticular soft-tissue rheumatic disorders of the neck and upper limb

OBJECTIVE

To critically review the criteria used to diagnose nonarticular soft-tissue rheumatic disorders of the neck and upper limb.

METHODS

An extensive search of the literature, including a search of Medline and EMBASE, authoritative recent reviews, and relevant textbooks, was completed. The diagnostic criteria used in epidemiologic studies were compared and the reliability and validity of these criteria were assessed.

RESULTS

Altogether, the search identified 117 relevant research articles, among which 69 included a physical examination component, but few specified diagnostic criteria. Evidence supported respectable levels of between-observer repeatability regarding: symptom questionnaires (kappa, 0.52 to 0.79); measurement of shoulder range of motion with a goniometer (intraclass coefficients > 0.70); tests for carpal tunnel syndrome (Tinel's and Phalen's kappa, 0.53 to 0.80); and demonstration of neck tenderness (kappa = 0.43). The Katz hand diagram, and combinations of physical signs of carpal tunnel syndrome, show reasonable sensitivity and specificity for that diagnosis but only among patients referred to specialists with that putative diagnosis; no such validity has been shown among the general population. Only 1 diagnostic examination schedule has published data on both the reliability and the validity of its criteria and diagnoses. For the remaining soft-tissue upper-limb disorders, diagnostic criteria rely apparently on face and content validity and reliability data have not been published.

CONCLUSION

Classification of specific disorders of the neck and upper limb requires a back to basics approach. At present, the diagnosis of most of these conditions relies heavily on the clinical opinions of investigators and there are insufficient data to indicate that these criteria are repeatable, sensitive, or specific. Recent European initiatives offer scope to follow a more disciplined approach, but more work is urgently required.

Carpal tunnel syndrome: pathophysiology and clinical neurophysiology

Carpal tunnel syndrome (CTS) is a constellation of symptoms associated with compression of the median nerve at the wrist. The pathophysiology of CTS is not fully understood but mechanical aspects of injury within the carpal tunnel are most likely. The issues of ischemia, mechanical trauma, ectopic impulse generation, demyelination, tendonitis, elevated carpal tunnel pressure, mechanical factors, small and large fiber involvement and the variability of symptoms are presented. Documentation of neurophysiologic abnormalities in the median nerve is helpful to establish the diagnosis for CTS. There are several types of clinical neurophysiologic evaluations of the median nerve across the wrist. Sensory and motor nerve conduction studies (NCS) of the median nerve segment across the wrist compared to another nerve segment that does not go through the carpal tunnel (i.e. median, radial, or ulnar) are the most sensitive and accurate techniques. Other neurophysiologic techniques used to document CTS include vibrometry threshold testing, current perception testing, Semmes-Weinstein monofilament testing and two-point discrimination. These techniques have considerable subjective components and have not been found to be as sensitive as traditional NCS.

Examination of patients for carpal tunnel syndrome sensibility, provocative, and motor testing

The value of a test for carpal tunnel syndrome (CTS) depends on the purpose of performing the test. When screening a large population with a low prevalence for CTS, a test with a high sensitivity is needed so that no possible case goes undetected. However, in order to establish a diagnosis, a more specific test is required. Using a combination of physical examination techniques, including sensibility and provocative testing, the probability of correctly diagnosing CTS without relying on electrodiagnostic studies can be very high. Because CTS is a clinical syndrome, the diagnosis should be made on clinical grounds. Electrodiagnosis is extremely important, however, in its ability to objectively document median nerve slowing and eliminate other competing differential diagnoses.

A systematic review of the clinical diagnostic tests for carpal tunnel syndrome

The purpose of this report was to critically review studies of the clinical diagnostic tests for carpal tunnel syndrome. The reports were located through Medline, Current Contents, related readings, and the reference lists of the articles. They all explored the use of clinical diagnostic tests for carpal tunnel syndrome compared with the results of NCS. Criteria for systematically reviewing the studies were developed, tested for reliability, and applied to the studies. Many studies did not have sufficient detail to allow repetition of the protocol by other researchers. The sensitivities and specificities reported for each can be compared with the quality criteria ratings they each received. The literature supports the use of the wrist flexion and carpal compression test and suggests that 2-point discrimination has low sensitivity for diagnosing carpal tunnel syndrome. Many reports do not include methodology, which makes the results difficult to reproduce and to apply to other populations. (J Hand Surg 2000; 25A:120-127.

Consensus criteria for the classification of carpal tunnel syndrome in epidemiologic studies

Criteria for the classification of carpal tunnel syndrome for use in epidemiologic studies were developed by means of a consensus process. Twelve medical researchers with experience in conducting epidemiologic studies of carpal tunnel syndrome participated in the process. The group reached agreement on several conceptual issues. First, there is no perfect gold standard for carpal tunnel syndrome. The combination of electrodiagnostic study findings and symptom characteristics will provide the most accurate information for classification of carpal tunnel syndrome. Second, use of only electrodiagnostic study findings is not recommended. Finally, in the absence of electrodiagnostic studies, specific combinations of symptom characteristics and physical examination findings may be useful in some settings but are likely to result in greater misclassification of disease status.

Lack of association between outcome measures of nerve regeneration

Studies of nerve regeneration in rodents utilize at least one of three classes of outcome measures: electrophysiology, morphometry, and functional tests. The assumption that these measures are correlated was tested utilizing a data set of 16 variables. Significant correlations (Spearman's rho, P < or = 0.05) were found within variable classes; however, none were found between classes. The three commonly utilized outcome measures do not measure the same phenomenon but rather discrete aspects of nerve regeneration.

Preliminary evaluation of a sensory and psychomotor functional test battery for carpal tunnel syndrome: Part 1--Confirmed cases and normal subjects

Two new computer-controlled functional tests were developed, known as the Wisconsin test battery, for carpal tunnel syndrome (CTS). The gap detection sensory test quantifies tactile thresholds for areas of the hand innervated by the median nerve. The rapid pinch and release psychomotor test measures the initiation and control of specific muscles innervated by the median nerve motor branch. Ten confirmed CTS patients (based on electrophysiological parameters and examination; 18 CTS hands) and eight confirmed normal subjects (16 hands) with a similar average age were administered both tests. The CTS patients showed significant functional deficits for both tactility and psychomotor tests. Average CTS performance was 24 to 104% poorer than for the normal subjects, depending on the performance measure. The results indicated high correlations (r = 0.5 to 0.8) between median nerve electrophysiological parameters and tactility or psychomotor performance variables. No single functional test variable had sufficient sensitivity for detecting CTS among the subject pool. The combination of the two tests using 95% confidence level cutoff points achieved a sensitivity of 0.78 and a specificity of 0.81. Stepwise discriminant analysis resulted in two performance variables capable of a sensitivity of 0.72 and a specificity of 0.94 for differentiating well-defined CTS subjects from normal subjects. Despite these promising results, limitations of the study include small sample size and subject selection bias. Further studies are needed for verifying the utility of the functional test battery for detecting CTS in a general population.

Screening for carpal tunnel syndrome in the workplace. An analysis of portable nerve conduction devices

Several devices have been developed for rapid motor or sensory median nerve conduction testing. We evaluated the validity and reliability of the Neurosentinel (NS) and NervePace (NP) electroneurometer for sensory and motor testing, respectively, compared with formal electrodiagnostic studies (EDS), and examined their potential role in workplace screening for carpal tunnel syndrome (CTS). Thirty-two working subjects without CTS were examined and tested with the NS, NP, and EDS, and retested one week later. Subjects were selected who did not have CTS, other hand or nerve problems, or jobs with significant ergonomic risks, in order to decrease the likelihood of changes over time in median nerve function. Mean correlations of NP and NS with EDS latencies ranged from r = 0.069 to r = 0.85, with somewhat better correlation for NS (sensory) than NP (motor). Test-retest reliability was greatest for motor EDS (r = 0.86 to 0.91) and similar for sensory EDS, NS, and NP (r = 0.72 to 0.79); mean results were very similar. Based on the observed relationship between NS or NP and EDS results, confidence intervals were calculated to represent the range of EDS results consistent with a single NS or NP measurement. These intervals ranged from +/- 0.3 milliseconds (ms) for NS to +/- 0.6 msec for NP, with similar ranges for change over time in an individual. The magnitude of these intervals for a single test or individual implies that the NS and NP are unlikely to identify individuals with CTS or to detect changes over time that are not accompanied by symptoms or signs. The screening devices are not likely to be useful in confirming early CTS, when single latency values may be normal, and detailed EDS may be necessary to detect nerve entrapment. Compared with EDS, these devices have moderate validity and similar reliability; they are probably most useful for cross-sectional or longitudinal studies of groups, but care must be taken in using them for pre-placement or surveillance tests of individual workers. False-positive results may lead to discrimination, inappropriate referrals and interventions; false-negative tests can result in inappropriate reassurance and missed opportunities for intervention.

Assessment of vibrotactile sensitivity in patients with carpal tunnel syndrome

The effectiveness of using vibrotactile threshold measures to aid in the diagnosis of carpal tunnel syndrome (CTS) was evaluated. Thresholds for detecting 1-, 10-, and 300-Hz vibratory stimuli were measured on the fingertips of 24 CTS patients and 20 healthy control subjects. There were no significant differences in threshold for 1- and 300-Hz between the two groups. Although there were significant differences for 10-Hz stimuli, the mean patient threshold was within 1 standard deviation of the mean threshold for the control group. These results indicate that threshold testing is not a suitable diagnostic tool for CTS. Additionally, we examined whether thresholds were elevated in the presence of pain. Seven patients reported experiences of pain and no pain sessions. No significant differences in threshold were found between the two pain conditions, indicating that the presence of pain related to CTS does not affect threshold.